On 06/02/2020 10:18 AM, John Hubbard wrote: > On 2020-06-01 21:20, Anshuman Khandual wrote: > ... >>> also important: maybe this patch should also be tracking other causes >>> of THP PMD migration failure, in order to get a truer accounting of the >>> situation. > > I hope one of the experts here can weigh in on that... > >> Is there any other failure reasons which are only specific to THP migration. >> Else, adding stats about generic migration failure reasons will just blur >> the overall understanding about THP migration successes and failure cases >> that results in splitting. >> > > Thinking about that: we do have PGMIGRATE_SUCCESS and PGMIGRATE_FAIL, so I > suppose comparing those numbers with the new THP_PMD_MIGRATION_SUCCESS and > THP_PMD_MIGRATION_FAILURE events should cover it. That is right. > > However, the fact that this is under discussion hints at the need for a > bit of documentation help. What do you think about adding some notes about > all of this to, say, Documentation/vm/page_migration.rst ? Sure but probably bit later. Because I am also planning to add couple of trace events for THP migration, hence will update the documentation part for both VM stat and trace events together.
